(1) Field of the Invention
The present invention relates to an ozone gas sensor and an ozone gas detecting device having the ozone gas sensor.
(2) Description of the Prior Art
A conventional ozone gas sensor comprises a film type semiconductor element including an insulating substrate such as of alumina and a semiconductor film consisting of a metallic oxide formed on the substrate, and a layer of silica formed on a surface of the film type semiconductor element. The semiconductor film of a metallic oxide allows ozone gas having high reactivity to reach a sensing section of the sensor without decomposing on the surface of the semiconductor film. The layer of silica formed on the semiconductor element promotes sensitivity to ozone gas.
Such an ozone gas sensor has the following problem when used in the presence of both ozone gas and a reducing gas:
Where the film type semiconductor element comprises an n-type semiconductor, the resistance of the semiconductor increases through contact with ozone gas and decreases through contact with the reducing gas, thereby rendering measurement results inaccurate. Conversely, where the film type semiconductor element comprises a p-type semiconductor, the resistance of the semiconductor decreases through contact with ozone gas and increases through contact with the reducing gas. In either case, measurement results are inaccurate, being lower than actual levels or dispersed.
Consequently, an ozone gas detecting device incorporating such an ozone gas sensor has low sensitivity and precision in the presence of a reduction gas.